Fume hood construction



Nov. 23, 1965 H. N. GRow ETAL FUME HOOD CONSTRUCTION 4 Sheets-Sheet 1Filed Feb. 21, 1963 102 Harig HIIIIIIIIIIIIIIJHIIIWM PFI INVENTORS, G T0LU,

l I l Il l Il Nov. 23, 1965 H.v N. GROW ETAL 3,218,953

FUME HOOD CONSTRUCTION Filed Feb. v2l, 1965 4 Sheets-Sheet 2 Nov. 23,1965 H. N. GROW ETAL FUME lHOOD CONSTRUCTION 4 Sheets-Sheet 5 Filed Feb.21. 1963 00 nuu0n0u0n0w000 00 0 0000 0 0 000000 0 0000 l0000000000000 00000 0000 00000000000 willi/lllIlI/ll/llll. Ill/llll//l INVENTORS. Af.Grof,

Harig BY Leo @Pula v @aad H. N. GROW I-:TAL

FUMEv HOOD CONSTRUCTION Nov'. 23, 1965 4 Sheets-Sheet 4 Filed Feb. 2l,1963 m .L n @m I I Im. I| A NI Il @Im 1 w InIWIJ. Ivl o o o o o o o AIII. III" N I I IL MMI .I Q 0 \O O O O "Il ll. D0 1 .JI II 000 o o wNI o oo "I+ Il. "II 00M I1 O 0 O 0 O I I IIN I OOQmOOOQN/ mn IT. \@N @I Im mI1 I I--- II IIPILIII n ...IIIIIIIIIIH I I I I I I I l l I I I I I I I ll l l l l fI. INSI IIIIIIIIIIIII m u b/Nnf. m u rf I RSI m m.PJQIIInw/I. .HIWWIIIH IIIIhrIIlHn .H un .U m n I im@ u mll "III" .nIIIIIhI" IIUIIIIIU" n .|||.||hm\"||||.|||||||||l|."llll||" n T l I I I Il I I I l I l I I I 4 l I I I I I I I I I I I I I I I l I I I L.

m 1 53 INVENTORS. HQTAZGTOZU, BY Leo PQS, 4%, y

United States Patent() Filed Feb. 21, 1963, Ser. No. 260,128 3 Claims.(Cl. 98-115) This invention relates to fume hoods, and, moreparticularly, to a fume hood for use in a chemistry laboratory and thelike.

It is a primary object of this invention to provide a fume hoodincluding novel means for introducing into the fume hood air taken fromthe room in which the hood is located as well -as air from an externalsource.

It is another object to provide a fume hood of the foregoing character,wherein air from an external source is introduced at the sides of anaccess opening of the hood.

Another object is to provide a hood of the foregoing character, havingmeans for evenly distributing air flow at the sides of the accessopening.

Still another object is to provide a fume hood having a novel baille forregulating the flow of air to an exhaust opening of the hood.

A still further object is to provide a fume hood of the foregoingcharacter, wherein the surfaces of the hood exposed to corrosive fumesare made of a non-corrodable material.

t Other objectsand advantages of the invention will become apparent fromthe following description taken in conjunction with the -accompanyingfigures of the drawings, in which:

FIG. 1 is -a front elevational view of a fume hood embodying theinvention;

FIG. 2 is an enlarged sectional view taken along the line 2 2 of FIG. 1;

FIG. 3 is an enlarged fragmentary sectional view taken on the line 3 3of FIG. 1;

FIG. 4 is an enlarged fragmentary sectional View taken on the line 4 4of FIG. l;

FIG. 5 is an enlarged fragmentary sectional view taken on the line 5 5of FIG. 2;

FIG. 6 is -a fragmentary sectional view similar to a portion of FIG. 2,showing an alternative form of the fume hood;

FIG. 7 is an enlarged fragmentary sectional view taken on the line 7 7of FIG. 6;

FIG. 8 is a front elevational view showing another alternative form ofthe fume hood; and

FIG. 9 is a sectional View taken on the line 9 9 of FIG. 8.

In general, a fume hood embodying the invention is a generally box-likeunit adapted to be positioned on a base, and comprises back, top and twoside walls. An exhaust opening is formed in the top wall'. A front wall,which forms an -air supply unit, has an access opening and a secondaryair inlet. Room air enters the access opening, and secondary air from anexternal source enters the air inlet and ilows through air passagewaysto an air outlet at the sides comprising the vertical and top sides ofthe access opening. Air from these two sources ioWs through the hood andout through the exhaust opening. Filter and screen assemblies arepositioned in the air outlets, 4and baffles lare positioned in the airpasageways to evenly distribute air flow through the air outlets.

vMounted within the structure between the access and exhaust openings isan -adjustable baie for regulating the llow of air through the hood. Theilow regulator baflle comprises upper and lower baflle sections, eachsection being mounted adjacent the back wall for pivotal Patented Nov.23, 1965 nce movement about a horizontal axis. The pivotal axis of theupper section is intermediate its top and bottom edges and the axis ofthe lower section is at its bottom edge. The top edge of the lowersection is exibly attached to the bottom edge of the upper section, andan air passageway is provided between the two sections. Ai-r passagewaysare also provided over and under the two balile sections, the relativesizes of the latter passageways being adjustable by pivoting the baillesections.

A sash assembly for closing the access opening and a light assembly mayalso be provided, and the interior inner surfaces of the hood exposed tocorrosive fumes may be made of non-corrodable material.

The fume hood shown in FIGS. 1 to 5 is indicated generally by thenumeral 10 and is adapted to be positioned on a base indicated generallyby the numeral 11. The hood 10 comprises a top wall 12, two side walls13 and 14, a back wall .16, and -a front wall 17. The upper surface ofthe base 11 forms a bottom wall for the hood 10.

Each side wall 13 and 14 comprises a substantially rectangular framemember 18 (FIG. 3) which may be formed yfrom a tubular material such asaluminum or steel, and a side panel 19 preferably made of anoncorrodable material. The side panels 19 are secured to the framemembers 18 preferably by bonding. If desired, an opening 21 may beformed in either or both side panels 19, which is normally closed by aremovable section 22 also preferably formed from a non-corrodablematerial. The section 22 is held in place in the opening 21 by twovertical cleats 23 and 24, and upper cleat 26 and a bottom cleat 27. Thevertical cleats 23 and `24 and the upper cleat =26 are secured to theoutside surface of the side panel 19 with a portion overlying section22. The bottom cleat 27 is secured -to the outside surface of thesection 22 with a portion overlying the panel 19. The upper edge of thesection 22 is secured to the top cleat 26 by screws 28, preferably madeof nylon. The section 22 may be taken out of the opening 21 by removingthe screws .28 and then tilting the section 22 inwardly and lifting itupwardly.

The back wall =16 comprises a back panel 31 (FIGS. 2 and 3) which ispositioned against the rearward edges of the side panels 19 and overliesthe rearward outer surfaces of the frame members 18. The back panel 31is secured to the frame members 18 by either bonding or by screws. Inthe event screws are used, they preferably do not extend into theinterior of the hood so that they cannot be reached by corrosive fumes.The back wall also preferably includes an angular member 32 having onearm secured to the outside lower edge of the back panel 31 `as bybonding, and its other arm seated on the upper surface of the base 11'.

The top wall 1|2 comprises a top panel 33 which overlies the uppersurface of the frame members 18 of the side Walls 13 and 14 and theupper edge of the back panel 31 of the back Wall 16, and is secured tothe frame members 18. The top panel 33 is also secured to one arm of anangle 35 which has its other arm secured to the back panel 3'1. The toppanel 33 has an exhaust opening formed therein adjacent the back wall16, and a cylindrical flange 34 may be provided around this opening forattachment to a duct of a blower system.

The front wall 17 forms an air supply unit, and has an access openingand a secondary air inlet formed in it. The front wall 17 comprises leftand right cornerposts 40 and 41 (FIGS. l and 3) secured to the sidewalls 13 and 14, respectively, and a center assembly 42 which eX- tendsbetween and is secured to the two vcornerposts 40 and 41. Eachcornerpost comprises an Iangle 43 (FIG. 3) which is seated against theforward and outer side surfaces of the adjacent frame member 18 andsecured thereto by a plurality of vertically spaced nut and boltcombinations 44. A column 46 is secured as by welding to the forwardside of each angle 43, the outer edge portion of each column 46 beingturned rearwardly as shown in FIG. 3. Each cornerpost also includes acover 47 which has a portion spaced forwardly of the column 46, and anouter portion which is also turned rearwardly and is secured as bywelding to the rearwardly turned edge portion of the column 46. The topand bottom edges of the column 46 and the cover 47 may be foldedinwardly as shown at 50 in FIG. 3, and the upper and lower ends of eachcornerpost may be enclosed by suitable plates 45.

As shown in FIG. l, the inner edges of the columns 46 and the covers 47of the two cornerposts 40 and 41 slant inwardly and upwardly from thebase 11 to the center assembly 42, these slanted edges of thecornerposts forming two sides of the `access opening. The surface of thebase 11 forms the bottom side of the access opening and the lower edgeof the center assembly 42 forms the top side of the access opening.

The space between the inner slated edges of the columns 46 and thecovers 47 form air outlets. With reference to FIGS. 2 and 5, a filter 48and a screen 49 are enclosed by a suitable frame 51 and positionedacross each outlet. The inner edges of the columns 46 and covers 47 maybe turned toward each other, and the frame 51 secured as by screws tothese inturned edges. The filter 48 may be made of a plurality of matterlayers of expanded metal. The screen 49 is also preferably made ofexpanded metal but having greater thickness and mesh than the filtermaterial and it is positioned such that its strands slant toward theinterior of the hood, as shown in FIG. 5. By this construction, whensecondary air passes through the outlets, it is directed into theinterior of the hood by the slanted strands. In FIG. 3, the filter andscreen assembly has been removed for convenience of illustration.

The center assembly 42 of the front wall 17 is above the access opening,and comprises an inner panel 53 (FIG. 2) secured at its vertical sideedges to the two columns 46, and an outer panel 54 spaced forwardly ofthe inner panel 53 and having its vertical side edges secured to the twocovers 47 of the cornerposts. The inner panel 53 is preferably made of anon-corrodable material. Further, the inner surfaces of the columns 46are also preferably lined with sheets S6 (FIG. 3) of noncorrodablematerial, and a non-corrodable corner brace 57 may be secured as bybonding to each side panel 19 and the adjacent corner brace 57.

The upper edge of the inner panel 53 is spaced below the upper edge ofthe outer panel 54, and a metal bracket 58 (FIG. 2) is secured to theinner panel 53 and extends up to the level of the upper edge of theouter panel 54. A top cover 59 is secured to the upper edges of theouter panel 54 and the bracket 58, the cover 59 enclosing the top of thefront wall 17 and having a secondary air inlet formed therein. A flange60 may be formed around this inlet opening.

At the Ibottom of the center portion 42, a filter 61 and a screen 62 areprovided which may be similar to the filter 48 and the screen 49 shownin FIG. 5. The filter 61 and the screen 62 may be mounted in a suitableframe and secured to the bottom edges of the back and front panels 53-and 54, and the strands of the screen 62 are formed to direct air intothe interior of the structure.

With reference to FIGS. 1 and 2, a horizontal distribnting ballie 63 isfastened to the inner and outer panels 53 and 54 for the purpose ofimproving the ow characteristics of secondary air flowing from the airinlet to the outlets at the sides of the access opening. The baffle 63has downturned forward and rearward edges which extend behind clips 64(FIG. 2) secured to the inner and outer panels 53 and 54. Thus thebaffle 63 may be removed simply by lifting it upwardly. Further, thisbaffle 63 may be perforated if desired.

When in use, the ange 60 is connected to an external source of secondaryair which may be air from outside the building, from a corridor, etc.This secondary air 1s supplied under pressure and ows through thepassageway formed between the inner and outer panels 53 and 54 of thefront wall 17, around the bafe 63 and out of the front wall 17 throughthe outlets at the sides of the access opening. The filters 48 and 61cause a slight back pressure to be built up within the air passageway ofthe front wall 17 by restricting the ow of air through them, and thisback pressure causes the liow of air through the three lters 48 and 61to be substantially evenly distributed. The screens 49 and 62 protectthe filters 48 and 61 and also direct the secondary air into theinterior of the hood. Due to the slanted inner edges of the columns 46and the covers 47, the cross sectional area of the air passageways atthe vertical-sides of the access opening is greater :at the top than atthe bottom of the access opening. Accordingly, the flow of air throughthe outlets in the vertical sides will be substantially evenlydistributed throughout the height thereof.y

The fume hood further includes a light assembly, indicated generally bythe numeral 70, for lighting the interior of the hood 10. The lightassembly 70 comprises a sheet 71, preferably made of a non-corrodablematerial, which has its end edges in abutment with and secured to theside panels 19 of the side walls 13 and 14, and its rearward edge inabutment with the panel 33 of the top wall 12. From the top panel 33,the sheet 71 slants downwardly and toward the front wall 17. An opening72 is formed in the sheet 71, and a pane 73 of translucent material suchas glass is positioned over the opening 72 on the upper side of thesheet 71 and is held in place by a bracket 74. Two generally V-shapedbraces 76 and 77 are secured to the outer surface of the sheet 71 at itsforward and rearward edges, the rearward brace 77 also being secured tothe undersurface of the top panel 33. The light assembly 7 0 furtherincludes a three bulb fiuorescent light fixture 78 having the outside ofits refiector secured to a bracket 79. The light fixture 78 iS supportedby a cover 81 which is secured to the bracket 79 and has a portionoverlying the top panel 33 of the top wall 12. The cover 81 is furthersecured by screws to the V-shaped bracket 76. The light fixture 78 maybe easily removed for maintenance simply by lifting the cover 81 and thelight assembly 78 out of the hood.

The flow of air through the fume hood is regulated by a baffle 8Smounted between the access opening of the front wall 17 and the exhaustopening of the top wall 33. The baffle 85 comprises an upper section 86adjacent the back wall 16 for pivotal movement about a horizontal axiswhich is intermediate its top and bottom edges, and a lower section 87mounted adjacent the back wall 16 for pivotal movement about ahorizontal axis which is adjacent its bottom edge.

The lower section 87 comprises a lower panel 88 and two lower pivotblocks 89 and 90 (FIGS. l and 2), the two pivot blocks 89 and 90 beingsecured to the lower corners of the lower panel 88. Preferably a slot isformed in the upper surface of each of the pivot blocks 89 and 90 whichreceives the bottom edge of the panel 88, and the pivot blocks 89 and 90are preferably bonded to the lower panel 88. The lower bafile section 87iis supported on two lower support blocks 92 and 93 which may be bondedto the side panels 19 of the side walls 13 and 14 at the lower rearcorners of the hood. Arcuate grooves are formed in the upper surfaces ofthe support blocks 92 and 93, and the lower surfaces of the pivot blocks89 and 90 are also arcuate and are seated in the grooves of the blocks92 and 93.

The upper baffle section 86 comprises an upper pivot strip 96 which issecured to the bottom and top edges of an upper panel 97 and anintermediate panel 98. The

which the lower and upper edges of the panels 97 and 98 extend, theseslots preferably being formed at an obtuse angle of, for example, 135The upper section 85 is positioned so that the lower panel 98 extendsgenerally downward toward the base 11 and the upper panel 97 slantsupwardly toward the top wall 12 and forwardly.

The upper pivot strip 96 extends across the entire width of the panels97 and 98, and is supported at its ends by two upper support blocks 99and 100 which are preferably secured to the side panels 19 of the sidewalls 13 and 14 by bonding. An arcuate groove is formed in the uppersurface of each block 99 and 100 which receives the lower arcuatesurface of the upper pivot strip 96. The upper corners of theintermediate panel 98 are recessed, as the points indicated generally bythe numeral 101 (FIG. 1), to provide space for the upper support blocks99 and 100.

The bottom edge of the intermediate panel 98 is attached to the top edgeof the lower panel 88 by a plurality of spaced apart llexible connectors102 (FIGS. 1 and 2). The connectors 102 maintain the adjacent edges ofthe panels 88 and 98 in iixed spaced apart relation.

The horizontal widths of the three panels 88, 97 and 98 and the upperpivot block 96 are made somewhat less than the distance between thes-ide panels 19 of the side walls 13 and 14 so that air gaps existbetween the vertical edges of the panels 88, 97 and 98 and the innersurfaces of the side panels 19.

The upper and lower baille sections 86 and 87 are pivotal from anintermediate position, indicated in full lines in FIG. 2, to a bottompanel closed position indicated by dashed lines in FIG. 2, and a bottompanel open position indicated by dash dot lines in FIG. 2. In the bottompanel closed position, the top edge of the lower panel 88 rests againstthe back panel 31 and the top edge of the upper panel 97 is spaced aconsiderable distance from the top wall 12. Air ilows to the exhaustopening over the top edge of the upper panel 97, through the spacebetween the bottom and top edges of the intermediate and lower panels 98and 88, and around the vertical edges of the upper and intermediatepanels 97 and 98. This position of the baille is preferable when lighterthan air fumes are to be exhausted since they tend to rise to the top ofthe hood. When heavier than air fumes are to be exhausted, the baillesections may be pivoted to the bottom panel open position where the topedge of the lower panel 88 is spaced a considerable distance from theback wall 16 and the top edge of the upper panel 97 engages the top Wall12. Fumes and air then flow through the space between the bottom edge ofthe lower panel 88 and the upper surface of the base 11 and the backpanel 31, through the space between the bottom and top edges of theintermediate and lower panels 98 and 88, and along the vertical edges ofthe three panels 88, 97 and 98. The fumes do not flow over the top edgeof the upper panel 97 since it engages the top wall 12. In theintermediate position, the top edges of the upper and lower panels arespaced from the panels of the top and bottom walls and air ilows aroundthe top and bottom edges of the baille and through the space between thebattle sections. The heights of the baille panels are preferably chosensuch that the adjacent edges of the intermediate and lower panels are atsubstantially the height of a beaker when mounted above a standardBunsen burner, and since the space between these two panels is alwaysopen, fumes from the beaker will be quickly withdrawn.

From FIG. 2 it will be noted that the center of gravity of the upperbaille section 86 is to the left of its horizontal axis of rotation,which produces a tendency of an upper baille section 86 to pivot in thecounterclockwise direction, and consequently the lower baille section topivot in the clockwise direction. To maintain the baille sections at aselected position, a baille latch (FIGS. 1 and 2) is provided. Thislatch 105 comprises a ratchet block 106 secured to the back panel 31 ofthe back wall 16 the block extending through a vertical slot 107 (FIGS.1 and 4) formed at the upper center of the lower panel 88. The ratchetblock 106 has a plurality of notches 108 formed in its upper surfacewhich receive a downwardly extending lip formed on the lower end of astop block 109. The stop block 109 is slidably mounted for movement in avertical direction within the slot 107 of the lower panel 88 by means oftwo vertically extending grooves 111 formed in opposite sides of thestop block 109, the vertical margins of the slot 107 extending into thegrooves 111. A handle 112 may be secured as by bonding to the forwardside of the stop block 109. To adjust the position of upper and lowersections of the baille 85, the handle 112 and the stop block 109 arelifted to an upward position where the lip of the stop block 109 is outof engagement with the ratchet block 106. The stop block 109 may then bemoved in either the forward or rearward direction until the sections ofthe bailles are in the desired position, and the stop block 109 is thenlowered to bring its lip into one of the grooves 108 of the ratchetblock 106. Since the ratchet block 106, in this instance, has iivegrooves 108, the baille 85 may be locked in any one of iive positionsincluding the three positions previously described.

The fume hood may also include a sash assembly mounted on the front wall17 for varying the amount of room air drawn into the hood and forclosing the access opening of the front wall when desired. Withreference to FIGS. 1 to 3, the sash assembly comprises a 'sash 120having a panel of glass 121 lsecured within a rectangular frame 122. Thesash is preferably constructed such that its inner surface, which may beexposed to corrosive fumes, is constructed entirely of a non-corrodablematerial. A column 123 is secured to the cover 47 of each cornerpost 40and 41, and the sash 120 is slidably mounted for movement in a verticaldirection within a slot formed between each column 123 and the adjacentcover 47 of the cornerpost. Guides 124 (FIGS. 2 and 3) are secured tothe vertical edges of the sash 120 as by screws, the guides 124 beingpositioned within the slots of the columns 123 and guiding the movementof the sash 120. Means is preferably provided for counterbalancing theweight of the sash 120, this means comprising a cord 126 (FIG. 2)attached at one end to each vertical side of the sash 120 and passedover the top of the pulley 127. The cords 126 are attached at theirother ends to weights 128 (FIG. 3). The pulleys 127 (FIG. 2) arerotatably mounted on the columns 123 adjacent their upper ends. A stop129 (FIG. 2) may be secured to each vertical edge of the Sash 120 andpositioned to engage a suitable strap (n-ot shown) secured to eachcolumn 123 adjacent its upper end and thereby limit the upward movementof the sash 120. Above the access opening of the lfront wall 17, thespace between the two columns 123 is preferably enclosed by a frontcover 130 (FIGS. 1`to 3) which extends ybetween and is secured to thetwo columns 123.

When the sash 120 is in the lowered position, substantially all of theair passing through the hood enters through the secondary outlets at thesides of the access opening. As the sash 120 is raised, the proportionof room air to secondary air entering the hood progressively increases.

FIGS. 6 and 7 show a portion of the front wall of a fume hood which maybe identical with the fume hood shown in FIGS. 1 to 5 with the exceptionthat the sash assembly and the columns 123 are eliminated. In theconstruction shown in FIGS. 6 and 7, room air always enters the hood inaddition to the secondary air entering the fume hood .through the airoutlets at the sides of the access opening.

FIGS. 8 and 9 show another alternative construction of the fume hood.This fume hood comprises a front wall 140, a back wall 141, a top wall142, two side walls 143 and 144, and a bottom wall formed by a base 145.The walls 141 may be identical with the corresponding walls of the hoodshown in FIGS. l to 6. An exhaust opening is formed in the top wall 142and is provided with a flange 146 which may be connected to an exhaustduct. A flow regulator baille 147 is mounted within the hood forregulating the llow of air to the exhaust opening. The baille 147 may bethe same as the baille 85 shown in FIG. 2 with the exception that aplurality of openings 14S may be formed in the lowermost panel toprevent fumes from accumulating at the forward surface of this panel.These openings 148 may be eliminated if desired. Further, a lightassembly 149 which may be identical with the light assembly 70 shown inFIG. 2, is preferably mounted at the juncture of the front and top walls140 and 142 for lighting the interior of the hood.

The front wall 140 is preferably secured to the two side walls 143 and144, and has an access opening, indicated generally by the numeral 151,and a secondary air intake 152 formed therein. The intake 152 may beconnected to a secondary air duct 153 extending from an external sourceof air under pressure. The front wall 140 has spaced apart front andback panels 154 and 155 which form an air passageway therebetweenleading from the secondary air intake 152 to the upper horizontal andtwo vertical sides of the access opening 151. A horizontal distributingbaille 157, which is preferably provided with perforations 158, ismounted within the air passageway below the secondary air intake 152.This baille 157 again may be removably mounted on clips (not shown) asshown in FIG. 2.

The access opening 151 on its upper horizontal and two vertical sides isseparated from the air passageway of the front wall 140 by screen andfilter assemblies. The numeral 159 indicates the screen and filterassembly for the upper horizontal side of the access opening 151 and thenumeral 161 indicates the screen and iilter assemblies for the twovertical sides of the access opening. The assemblies 159 and 161 are thesame as those shown in FIGS. 2 and 5. A double thickness of filtermaterial may be provided in the upper assembly 159 to increase therestriction of air flow at the upper side of the access opening 151 andthereby improve the air ilow characteristics at the vertical sides ofthe access opening 151. Further, a plurality of pressure control bales162 and 163 are preferably mounted in the portion ofthe air passagewayadjacent each vertical side of the access opening 151. The bafiles 162and 163 are preferably perforated, and the ballles 162 slope upwardlyfrom the front panel 154 in the direction of the back panel 155 whilethe baffles 165 slope downwardly from the front panel 154 toward theback panel 155, the baflles 162 and 163 thus having a zig-zagarrangement. The edges of the adjacent batlles 162 and 163 preferablyengage each other, and are provided to ensure a satisfactory -secondaryair llow pattern at the vertical sides of the access opening 151.

Where the use of a non-corrodable material is referred herein, acomposition comprising Portland cement and asbestos fibers mixed withacid resisting bond and filter is preferred.

We claim:

1. A fume hood comprising front, back, top and two side walls securedtogether in a box-like conguration, said top wall having an exhaustopening formed therein and said front wall having an access openingformed therein, and a baille mounted between said access and exhaustopenings, said baille comprising upper and lower sections each in theform of a generally rectangular panel, horizontal pivot means mounted onadjacent walls adjacent said back wall for mounting said upper and lowersections, said pivotal means for said upper section being intermediateits top and bottom edges and the pivotal axis of said lower sectionbeing adjacent its bottom edge, and a plurality of flexible connectormeans spaced along the adjacent edges of said upper and lower sectionsand holding said sections in spaced relation to form a gap, the bottomedge of said lower section being spaced from said back wall and the topedge of said lower section being movable into and out of engagement withsaid back wall on pivoting said lower section to the control flow of airfrom the lower part of the hood, and the top edge of said upper sectionbeing movable into and out of engagement with said top wall on pivotingsaid upper section to control the ilow of air from the upper part ofsaid hood.

2. A fume hood as in claim 1, wherein the bottom edge of said uppersection is spaced forwardly of the top edge of said lower section topermit flow of air therebetween for all pivoted positions of saidsections, the llow of air from the upper and lower parts of the hoodbeing inversely variable by pivoting said upper and lower sections.

3. A fume hood as in claim 1, and further including an adjustable latchmeans comprising a part secured to one of said walls of said fume hoodand a part mounted on one of said sections for holding said baille in anadjusted position.

References Cited by the Examiner UNITED STATES PATENTS 2,549,042 4/ 1951Angermueller 98-115 2,627,220 2/195 3 Morrow 98--115 2,704,505 3/ 1955Morrison 98-115 3,021,776 2/1962 Kennedy 98-115 3,111,077 11/1963Cortright 98-115 ROBERT A. OLEARY, Primary Examiner.

1. A FUME HOOD COMPRISING FRONT, BACK, TOP AND TWO SIDE WALLS SECUREDTOGETHER IN A BOX-LIKE CONFIGURATION, SAID TOP WALL HAVING AN EXHAUSTOPENING FORMED THEREIN AND SAID FRONT WALL HAVING AN ACCESS OPENINGFORMED THEREIN, AND A BAFFLE MOUNTED BETWEEN SAID ACCESS AND EXHAUSTOPENINGS, SAID BAFFLE COMPRISING UPPER AND LOWER SECTIONS EACH IN THEFORM OF A GENERALLY RECTANGULAR PANEL, HORIZONTAL PIVOT MEANS MOUNTED ONSAID UPPER AND ADJACENT SAID BACK WALL FOR MOUNTING SAID UPPER AND LOWERSECTIONS, SAID PIVOTAL MEANS FOR SAID UPPER SECTION BEING INTERMEDIATEITS TOP AND BOTTOM EDGES AND THE PIVOTAL AXIS OF SAID LOWER SECTIONBEING ADJACENT ITS BOTTOM EDGE, AND A PLURALITY OF FLEIXBLE CONNECTORMEANS SPACED ALONG THE ADJACENT EDGES OF SAID UPPER AND LOWER SECTIONSAND HOLDING SAID SECTIONS IN SPACED RELATION TO FORM A GAP, THE BOTTOMEDGE OF SAID LOWER SECTION BEING SPACED FROM SAID BACK WALL AND THE TOPEDGE OF SAID LOWER SECTION BEING MOVABLE INTO AND OUT OF ENGAGEMENT WITHSAID BACK WALL ON PIVOTING SAID LOWER SECTION TO THE CONTROL FLOW OF AIRFROM THE LOWER PART OF THE HOOD, AND THE TOP EDGE OF SAID UPPER SECTIONBEING MOVABLE INTO AND OUT OF ENGAGEMENT WITH SAID TOP WALL ON PIVOTINGSAID UPPER SECTION TO CONTROL THE FLOW OF AIR FROM THE UPPER PART OFSAID HOOD.